八选一须具选择器：用CASE语句。
LIBRARY E; USE IEEE.D_LOGIC_1164.ALL; EITY mux_8_1 IS PORT (A,B,C,D,E,F,G,H,En:IN STD_LOGIC; S:in STD_LOGIC_vector(2 downto 0); Y: out STD_LOGIC); end mux_8_1; ARCHICTURE mux OF mux_8_1 IS begin process( S,A,B,C,D,E,F,G,H,En) begin if En='0' then case S is when "000" => Y<=A; when "001" => Y<=B; when "010" => Y<=C; when "011" => Y<=D; when "100" => Y<=E; when "101" => Y<=F; when "110" => Y<=G; when "111" => Y<=H; end case; end if; end process; end mux;
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